Optical recording medium having two superimposed recording levels and corresponding recording device and reading process

Abstract

An optical recording medium including a first recording level including a first active film having amorphous areas and crystalline areas, the first recording level being configured to produce a phase difference between an optical beam reflected by the amorphous areas and an optical beam reflected by the crystalline areas; and a second recording level superimposed on the first recording level and including a second active layer with first areas and second areas, the second recording level being configured to produce an intensity difference between an optical beam reflected by the first areas and an optical beam reflected by the second areas.

We claim: 
     
       1. An optical recording medium comprising: a first recording level comprising a first active film configured to have amorphous areas and crystalline areas, wherein said first recording level is configured to produce a phase difference between an optical beam reflected by said amorphous areas and an optical beam reflected by said crystalline areas; and   a second recording level superimposed on the first recording level and comprising a second active layer configured to have first areas and second areas, said second recording level being configured to produce an intensity difference between an optical beam reflected by said first areas and an optical beam reflected by said second areas.   
     
     
       2. The recording medium according to claim 1, further comprising two dielectric films configured to sandwich said first active layer. 
     
     
       3. The recording medium according to claim 1, further comprising a transparent spacer configured to separate said first and second recording levels. 
     
     
       4. The recording medium according to claim 1, further comprising a transparent substrate configured to support said first recording level. 
     
     
       5. The recording medium according to claim 1, further comprising a reflecting film configured to cover said second recording level. 
     
     
       6. The optical recording medium according to claim 1, wherein said second active layer comprises a phase change material, said first and second areas of said second recording level being respectively amorphous areas and crystalline areas. 
     
     
       7. The optical recording medium according to claim 1, wherein said second active layer comprises a magnetooptical material, said first and second areas of said second recording level having different magnetization directions. 
     
     
       8. The optical recording medium according to claim 1, wherein said phase difference produced by said first recording level is about 90°. 
     
     
       9. The optical recording medium according to claim 4, wherein said two dielectric films have thicknesses so that said phase difference produced by said first recording level is about 90°. 
     
     
       10. The recording medium according to any one of claims 2 to 5 or 1 to 9, comprising a substrate having a first face covered by said first recording level and a second face covered by said second recording level. 
     
     
       11. An optical recording medium comprising: a first recording level comprising a first active film having amorphous areas and crystalline areas, said first recording level being configured to produce a phase difference between an optical beam reflected by said amorphous areas and an optical beam reflected by said crystalline areas; and   a second recording level superimposed on the first recording level and comprising a second active layer having first areas and second areas, said second recording level being configured to produce an intensity difference between an optical beam reflected by said first areas and an optical beam reflected by said second areas.   
     
     
       12. The optical recording medium according to claim 11, wherein said second active layer comprises a phase change material, said first and second areas of said second recording level being respectively amorphous areas and crystalline areas. 
     
     
       13. The optical recording medium according to claim 11, wherein said second active layer comprises a magnetooptical material, said first and second areas of said second recording level having different magnetization directions. 
     
     
       14. The recording medium according to claim 11, further comprising two dielectric films configured to sandwich said first active layer. 
     
     
       15. The recording medium according to claim 11, further comprising a transparent spacer configured to separate said first and second recording levels. 
     
     
       16. The recording medium according to claim 11, further comprising a transparent substrate configured to support said first recording level. 
     
     
       17. The recording medium according to claim 11, further comprising a reflecting film configured to cover said second recording level. 
     
     
       18. The recording medium according to any one of claims 11 to 17, comprising a substrate having a first face covered by said first recording level and a second face covered by said second recording level. 
     
     
       19. The optical recording medium according to claim 11, wherein said phase difference produced by said first recording level is about 90°. 
     
     
       20. The optical recording medium according to claim 14, wherein said two dielectric films have thicknesses so that said phase difference produced by said first recording level is about 90°.